Anhydroerythritol (AnEryt) shares some of its ligand properties with furanosides and furanoses. Its bonding to silicon centers of coordination number four, five, and six was studied by X-ray and NMR methods, and compared to silicon bonding of related compounds. Diphenyl(cycloalkylenedioxy)silanes show various degrees of oligomerization depending on the diol component involved. For example, Ph(2)Si(cis-ChxdH(-2)) (1) and Ph(2)Si[(R,R)-trans-ChxdH(-2))] (2; Chxd = cyclohexanediol) are dimeric, Ph(2)Si(AnErytH(-2)) (3) is monomeric, and Ph(2)Si(L-AnThreH(-2)) (4; AnThre = anhydrothreitol) is trimeric both in the solid state and in solution. Ph(2)Si(cis-CptdH(-2)) (5) (Cptd = cyclopentanediol) is monomeric in solution but dimerizes on crystallization. Si(AnErytH(-2))(2) (6) and Si(cis-CptdH(-2))(2) (7) are monomeric spiro compounds in solution but are pentacoordinate dimers in the crystalline state. Pentacoordinate silicate ions are found in A[Si(OH)(AnErytH(-2))(2)] (A = Na, 8 a; Rb, 8 b; Cs, 8 c). Related compounds are formed by substitution of the hydroxo by a phenyl ligand. K[SiPh(AnErytH(-2))(2)]1/2 MeOH (9) is a prototypical example as it shows the two most significant isomers in one crystal structure: the syn/anti and the anti/anti form (syn and anti define the oxolane ring orientation close to, or apart from, the monodentate ligand, respectively). syn/anti Isomerism generally rules the appearance of the NMR spectra of pentacoordinate silicates of furanos(id)e ligands. NMR spectroscopic data are presented for various pentacoordinate bis(diolato)silicates of adenosine, cytidine, methyl-beta-D-ribofuranoside, and ribose. In even more basic solutions, hexacoordinate silicates are enriched. Preliminary X-ray analyses are presented for Cs(2)[Si(CydH(-2))(3)] 21.5 H(2)O (10) and Cs(2)[Si(cis-InsH(-3))] cis-Ins8 H(2)O (11) (Cyd = cytidine, Ins = inositol).

The C4, C5, and C6 sugar alcohols erythritol (Eryt), D-threitol (D-Thre), D-arabitol (D-Arab), ribitol (Ribt), xylitol (Xylt), dulcitol (Dulc), and D-mannitol (D-Mann) form chelate complexes upon dissolution in Pd-en, an aqueous solution of [Pd(II)(en)(OH)2]. Stability rules are derived from the proportion of a respective species in the solution equilibrium. Crystal-structure analysis supports the NMR spectroscopic results for a series of binuclear compounds that contain the sugar alcohols as tetraanionic polyolato ligands: [Pd2(en)2(ErytH(-4))] x 10 H2O, [Pd2(en)2(D-Arab1,2;3,4H(-4))] x 7 H2O, [Pd2(en)2(Xylt1,2;3,4H(-4))] x 4 H2O, [Pd2(en)2(D-Mann1,2;3,4H(-4))] x 5 H2O, and [Pd2(en)2(Dulc2,3;4,5H(-4))] x 6 H2O. In the case of the pentitols and hexitols, the metalated tetraanions are stabilized by intramolecular hydrogen bonds. The hydrogen bonds uniformly connect an alkoxide acceptor to the hydroxy donor group located at the delta carbon atom. As a consequence of hydrogen bonding, the open-chain carbohydrate ligands become rigid. Crystal-structure analysis provides information on the configurational requirements for rigidity. According to these rules, the hydrogen-bond-supported Dulc2,3;4,5H(-4) tetraanion provides a geometrically persistent ligating pattern. Intramolecular hydrogen bonding seems to be the most-competitive variable to metalation of a polyol. [Pd2(tm-2,1:3,2-tet)(OH)3]OH (tm-2,1:3,2-tet = 1,3-bis(2'-dimethylaminoethyl)hexahydropyrimidine) is a metallizing agent that can force full metalation even in a case as intractable as that of dulcitol. Accordingly, [Pd4(tm-2,1:3,2-tet)2-(DulcH(-6))]Cl2 x 16 H2O contains the fully deprotonated hexitol as the ligand.

Anders als kürzlich behauptet ist das zwitterionische Bis(diolato)silicat 1 bei pH 7–8 nicht erstaunlich hydrolysestabil. Dies ergab eine genauere Analyse der 29Si‐ und 13C‐NMR‐spektroskopischen Daten von 1 unter einer Vielzahl unterschiedlicher Bedingungen (Lösungsmittel, pH, Konzentration), nach der in Lösung vor allem Hydrolyseprodukte vorliegen.

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[mer-(dien)(NO)Ru(AnErytH -2 )]BPh 4 ·2 H 2 O (1), [mer-(dien)

NH 3 ) 2 Pd II (OH) 2 ] reacts with the diol functions of erythritol. The solution equilibrium was analyzed by means of 13 C NMR spectroscopy. The main species in Pdrich solutions is the doubly metallated complex, which has been isolated in the form of yellow crystals of the formula [{(NH 3 ) 2 Pd II } 2 (l-ErytH ±4 )]´2 H 2 O (1). As minor solution species, monometallated complexes with 1,2-ErytH ±2 and 2,3-ErytH ±2 ligands were detected. Compared with the ethylenediamine analogue, [(NH 3 ) 2 Pd II (OH) 2 ] is a remarkably bad cellulose solvent despite its good coordinating ability. Extensive hydrogen bonding, which may not be expected for en ligands for steric reasons, from the ammine ligands to the deprotonated alkoxide functions ± resulting in lateral aggregation of the polysaccharide chains ± seems to be the molecular origin of this phenomenon.

Contrary to a recent claim that the zwitterionic bis(diolato)silicate 1 exhibits remarkable hydrolytic stability at pH 7–8, a closer look at 29Si and 13C NMR spectroscopic data of 1 under various conditions (solvent, pH, concentration) reveals that hydrolysis products are the predominant species in solution.

A conspicuous detail of the so‐called brown‐ring test (the analytical test on nitrate) is the reddish color of the bottom layer of concentrated sulfuric acid, which develops upon the bleeding of the brown layer into the acid. Crystals of the same color form from a solution of ferrous sulfate in concentrated sulfuric acid on saturation with gaseous nitric oxide. The structure of this H3O[{Fe(NO)(μ4‐SO4)(μ2‐SO4)0.5}n/n] (1a) is made up from infinite chessboard‐type layers with sulfur on the field junctions and Fe(NO) moieties below the black and above the white fields. An Fe–N–O angle of about 160° causes disorder in the tetragonal space group I4/mmm. A similar crystal pathology was found in the related [{Fe(MeOH)(NO)(μ4‐SO4)}n/n] (1b) in the same crystal class. A one‐dimensional coordination polymer is formed in crystals of a third compound that comprises the Fe(NO)O5 coordination pattern, namely the brown oxalato species [{Fe(H2O)(NO)(μ2‐ox)}n/n·H2O] (2). A still larger NO tilt of about 156° is not obscured by disorder in the triclinic crystals of 2.